Process for carbonizing coal



Jan. 7, 1941. G. w. WALLACE PROCESS FOR CARBONIZING COAL Filed Feb. 25,1958 3 Sheets-Sheet 3 Flc, 9.

INVENTOR Patented Jan. 7, 1941 UNITED f srA'rEs 4 claims.

This invention relates to the carbonization of coal and similar solidcarbonaceous substances and its principal object is to provide animproved process of and apparatus for effecting the carbonization ofcoking or semi-coking coal' and it is primarily adapted to carbonizingslackcoal or screenings and more particularly adapted to carbonizing thene coal and dust resulting from the preparation of so called stoker fuelwhere the product is often as fxneas a minusten mesh material. A

Another object of the invention is the production of smokeless fuel bylow temperature car' bonization. A further object of the invention isthe tion of a smokeless fuel under conditions wherein the volatilecontent of the resultant product may be controlled within close limitsto that desired. And still another object isthe production of a lowtemperature smokeless fuel vof improved structure and denseness.

Other objects and desirable features of the invention will behereinafter pointed out.

In the present invention the process of carbonizing coal consistsin'causing the coal to pass Athrough a carbonization chamber supportedon a moving or movable pan or apron conveyor, regulating the depth ofcoal in the pans or thickness of layer on the apron to that desired andcovering the coal in the pans or layer on the aprons with a series ofcovers of sufficient weight to affect the structure and compactness ofthe resultant fuel product and heating the coal undergoing carbonizationfrom beneath the supporting medium and above the covers with hot gaseousproducts of combustion in direct contact with a. bustion are controlledby using an excess of gasl where gases are burnedwith air to producesaid hot gaseous products of combustion.

Figure 1 of the drawings is a vertical sectional view of one form ofapparatus that can be vused in practicing the present process. ThesectionI (Cl. 2oz-26) 3-3 and illustrates the manner in which thalinkssupport the pans.

I Figure 4 is a vertical cross sectioni,v of the ap`- "paratus on line4-4 Fig. 1 and illustrates the manner in which the hot combustion gasesare admitted to the carbonization chamber.

Figure 5' is a vertical cross section of the apparatus on line 5 5 Fig.1 and illustrates the manner in which the hotl combustion gases leavethe chamber. L*

Figure 6 is a broken vertical sectional view of another form oi appartus which can be used in practicing the presen 'invention andillustrates one type of apron conveyorwhich may be used.

Figure 7 is a vertical section in part onl line 1-1Fig. 6. No

Figure 8 is an enlarged view of the driving sprocket illustrating themanner in which the covers may be brought into position and` placed ontop of the coal.

.Figure 9 is a cross sectionthrough line 9-9 Fig. 6 and illustrates adamper'control of'the hot gaseous products of combustion.

sist either of shallow pans or an apron conveyor,l

a series of more or less loosely riding covers C which are arranged tocover the coal in'the pans or on the apron conveyor. and which are ofsufllcient weight to affect` the structure of the carbonized residue orsmokeless fuel. The rsaid supporting medium and covers may beconstructed of steel, cast steel, cast ironor a special alloy of ironhaving heat resisting properties, usually two or more of such metalswill be used in assembling the apparatus; A coal hopper D is providedfrom which the coal to be carbonized is fed onto thepans or onto theapron conveyorat the desired depth or thickness. In the apparatussprocket wheels E actuate the conveyor and sprocket wheels E which aresynchronized with sprockets E actuate the covers, tail sprockets F andF' reverse the direction of the conveyor and covers to the point ofloading. Links G carry the weight of thepans or aprons and in turn aresupported by rods H which are connected with wheelsI' which travel onrails J, links G carry the covers excepting when they are resting on thecoal and are supported by rods H' and wheels I which travel'on rails J.A driving gear K, preferably of variable speed is provided to actuatethe sprocket wheels Eand E' said driving gear may be powered in anysuitable manner for instance by an electric motor K'. In the apparatusas illustrated means are provided for admitting hot products ofcombustion beneath the coal supporting medium and above the covers at Lthrough a series of ilues M below the supporting medium and through aseries of flues M' above the covers. 'Ihe hot gaseous products ofcombustion after passing through the ues M and M' leave thecarbonization chamber at N from which they are conducted to the desiredcondensing and scrubbing apparatus not shown. 'I'he product of thecarbonization or smokeless fuel is discharged from the conveyor orsupporting medium into the hopper O from which it is removed from thecarbonization chamber by means of star feeder P which serves also toprevent any airI entering the chamber at this point. It is to beunderstood that the hopper O may be of any desired size. With certaincoals it may be desirable to use the apron conveyor or supporting mediumB Fig. 6 which provides means X for assisting in the removal of thecarbonized residue from the supporting medium. In the apparatus R Fig. 1is a refractory top and bottom for flues M and M which if desired may bedispensed with. In Figs. 1 and 2 the ilues M and M' are shown as crossflues which conduct the hot combustion gases backand forth across andbeneaththe supporting medium and above the covers from the inlet L asshown in Figs. 2 and# to the outlet N as shown in Figs. 2 and 5.

' Fig: 6 illustrates a single longitudinal open flue S beneath theysupporting medium and S above the covers, in this illustration the topand bottom refractory lining R as shown in Figs. 1, 4 and 5 is omitted.In order to control the hot combustion gases entering and leaving theopen ues S and S' bailies T and T' may be provided at the inlet andoutlet of said iiues the bailles having a series of ports which may beadjusted by partially opening' or closing dampers U and`U' as shown inFig. 9, By the use of these dampers the hot combustion gases enteringthe carbonization chamber beneath the supporting medium and above thecovers at inlet L and leaving the chamber at outlet N may be distributeduniformly below and above the coal being carbonized.

While two different systems of ilues have been illustrated otherarrangements of passing the hot combustion gases used toeiect thecarbonization into and through the carbonization chamber,

may be used and in some cases it may be desirable Ato effect thecarbonization by passing the hot combustion gases beneath the supportingmedium only, this would apply particularly to cal having unusualswelling and plastic characteristics. The hot gaseous products ofcombustion used to effect the carbonization are preferably admitted tothe carbonization chamber at the discharge end of the coal supportingmedium, and caused to pass in countercurrent to the direction ofmovement of the coal through the chamber, and removed from the end wherethe coal is fed onto the supporting medium.

In synchronising the placing of the covers on the coal short rails VFig. 3 may be used to guide the covers as they leave sprockets E' andposition them properly on the coal after which the full weight of thecovers, links, rods and wheels 'will be on the .coal body during thecarbonization period until short guide rails Vv pick the weight up asthe covers reach sprocket wheels F', or the modification shown in Figs.6 and 8 may be used ln which case the covers are positioned over thecoal either on the pans or aprons of the conveyor directly from sprocketwheels E' which are synchronized with sprocket wheels E and as thesupporting medium and covers move forward into the carbonization chamberthe weight of the covers is transferred to the coal due to the slots Wshown in Figs. 6, 7 and 8 moving up on rods H' freeing the covers fromany support until they are lifted from the carbonized residue bysprocket wheels F'.

Other means of placing the covers on the body of coal being carbonizedand properly synchronising the same with the body of coal on thesupporting medium may be used, the drawings illustrating two practicalmethods.

The primary object of the covers is to compress the coal duringcarbonization particularly while it is passing through the plastic stageso as to produce as dense and compact a product as possible.

The coal or material to be carbonized may be passed through thecarbonization chamber either continuously or intermittently, it may beadvanced through the chamber for short distances at frequent intervalsor through substantial distances with correspondingly long stationaryperiods between the intervals of movement. While the continuous movementof the material through the chamber is preferable the intermittentmovement is entirely practical.

The hot gaseous products of combustion used to effect the carbonizationare preferably produced entirely outside the carbonization chamber byburning gases with air the gases being in excess of the amount of airrequired for the theoretical complete combustion of the same. Thetemperature of the hot gaseous products of combustion is controlled bythe amount of excess gas used, i. e., 60 parts of a 120 B. t. u. gas and40 parts air will furnish products of combustion having a lowertemperature than when using 50 parts gas and 50 parts air, by using thismethod of regulating the carbonization and controlling the temperature`of the gaseous products of combustion used to effect the carbonizationtemperatures of 550C. to 800 C. may be maintained uniformlly, and higheror lower temperatures may be secured and controlled if desired, thegreater the amount of excess gas used the lower is the temperature ofthe products of combustion. The -hot gaseous products of combustion arepreferably of a reducing nature as this condition serves to protect themental portions of the apparatus. While a less desirable result would besecured it is possible to have the combustion of the gases take .placepartially within the carbonization chamber.

The gases resulting from the operation of the process are usuallysucient in amount and quality to furnish the hot gaseous products ofcombustion used to effect the carbonization. If for any reason it is notdesirable to use the gases resulting from the operation of -the processproducer gas may be used or any other combustible gas or fuel or afurnace may be installed to furnish the hot gaseous products ofcombustion. If de`- sired instead of using an excess of gas to controlthe temperature of Vthe hot gaseous products of combustion the same maybe controlled by admixing or diluting with inert gas and/or steam or thetemperature may be controlled in any other 1 and 6, the gate Y shown inFig. 1 may if desired be arranged so as to bring thelevel of the coal inthe pans to a point level with or just below the top of the pans, thegate Y as shown in Fig. 6 may be adjusted so as to control the thicknessof the layer or body of coal to that desired.

The thickness of the layer or body of coal may Vary considerably withdifferent coals however a thickness of from three to four inches shouldmeet any usual requirements as relatively thin layers will carbonizemore eiciently.

In practicing the process of the present invention a layer of coal ofthe desired thickness is fed from hopper D on to the moving or movableconveyor or supporting medium B which enters the carbonization chamberwithin A where the coal is covered and compressed by covers C. Hotgaseous products of combustion are passed beneath the supporting mediumand above the covers to eiect the carbonization of the coal at atemperature of from 550 C. to 650 C. for low temperature carbonizationwhere around 8 to 12% volatile matter is desired in the resultant fueland at higher temperatures where a lower amount of volatile matter iswanted. The rate at which the coal travels through the chamber isadjusted so that the carbonization is complete when the residue isdischarged into hopper O from which it is removed through sealing deviceand feeder P and, from which point it is cooled and taken to storage.

The gases, oils and liquids distilled from.the coal during carbonizationescape around or through the covers which may be perforated if desiredand between the sections of the supporting medium and they are removedfrom the carbonization chamber entrained with the hot gaseous productsof combustion. The combined gases may be cooled and washed in any mannerdesired to remove such of the coal tar and other byproducts as it may befound protable or desirable to recover. An exhauster may be used toremove the gases and vapors from the carbonization chamber under apartial vacuum and deliver them under pressure to the condensers orplace oi use. The amount of gas required to eect the carbonization mayif desired be returned to a combustion chamber which may form a part ofthe carbonizing apparatus where it is burned with air to produce the hotgaseous products o cornbustion, the temperature of said products beingcontrolled and regulated in the manner described. The excess gasproduced in the operation of the process and not used for carbonizationpurposes may beused otherwise or may be wasted.

T. claim:

1. The process of carbonizdng csr coal to produce a substantiallysmokeless fuel which consists in confining the coal in shallow pans, andcontinuously passing the panned coal in a substantially horizontaldirection through a hot carbonizing chamber, the coal being confinedacross its upper .surfaces by loosely riding covers of suincient Weightto produce a relatively small-pored dense coke while permitting escapeof the gaseous products of such carbonization.

2. The process of carbonizing coking coal to produce a substantiallysmokeless fuel which consists in conning the coal in shallow pans, andcontinuously passing the panned coal in a substantially horizontaldirection through a hot carbonizing chamber, having a temperature rangefrom 550 C. to 800 C., the coal being conned across its upper surfacesby loosely riding covers of sumcient weight to produce a relativelysmallpored dense coke while permitting escape of the gaseous products ofsuch carbonization.

3. The process of carbonizing coking coal to produce a substantiallysmokeless fuel which consists in confining the coal in shallow pans,continuously passing the panned coal in a substantially horizontaldirection through a carbonzing chamber, the coal being coniined acrossits upper surfaces by loosely riding covers of suicient weight toproduce a relatively small-pored dense coke while permitting escape ofthe gaseous products of such carbonization, and passing hot gaseousproducts of combustion through the chamber in a direction opposite tothe direction of movement of the coal, said products of combustion beingproduced by burning combustible gases with air in an amount insulcientfor their complete combustion.

4.. The process of carbonizing coking coal to produce a substantiallysmokeless fuel which consists in conning the coal in shallow pans,continuously passing the panned coal in a substantially horizontaldirection through a carbonizing chamber, the coal being conned acrossits upper surfaces by loosely riding covers of sufficient weight toproduce a relatively smallwpored dense coke whiie permitting escape ofthe gaseous prod1 ucts of such carbonization in a serpentine pathgenerally counter-current to the movement of the coal, and passing hotgaseous products of come bustion through the chamber in a direction opposite to the direction oi movement of the coal, said products ofcombustion being produced by burnn ing combustible gases with air in anamount inB sumcient for "their complete combustion.

GEORGE W. WALLACE.

